A study of the photophysical properties of nitrogen-vacancy (NV) color centers in diamond nanocrystals of size 50 nm or below is carried out by means of second-order time-intensity photon correlation and cross-correlation measurements as a function of the excitation power for both pure charge states, neutral and negatively charged, as well as for the photochromic state, where the center switches between both states at any power. A dedicated three-level model implying a shelving level is developed to extract the relevant photophysical parameters coupling all three levels. Our analysis confirms the very existence of the shelving level for the neutral NV center. It is found that it plays a negligible role on the photophysics of this center, whereas it is responsible for an increasing photon bunching behavior of the negative NV center with increasing power. From the photophysical parameters, we infer a quantum efficiency for both centers, showing that it remains close to unity for the neutral center over the entire power range, whereas it drops with increasing power from near unity to approximately 0.5 for the negative center. The photophysics of the photochromic center reveals a rich phenomenology that is to a large extent dominated by that of the negative state, in agreement with the excess charge release of the negative center being much slower than the photon emission process.

In this paper, we report the characteristics of InAs/InP quantum dashes (QDash) based lasers emitting around 1.55 μm. An unprecedented high modal gain of ∼100 cm−1 is obtained for an optimized active structure by stacking 12 QDash layers. Directly modulated lasers allowed achieving a modulation bandwidth of ∼10 GHz and a Henry factor around 5. Thanks to p-type doping, the Henry factor value is reduced down to 2.7 while the modulation bandwidth still amounts to ∼10 GHz. This shows that doping of the active region is important to improve the dynamic characteristics of QDash lasers.

We review our recent developments of near-field scanning optical microscopy (NSOM) that uses an active tip made of a single fluorescent nanodiamond (ND) grafted onto the apex of a substrate fiber tip. The ND hosting a limited number of nitrogen-vacancy (NV) color centers, such a tip is a scanning quantum source of light. The method for preparing the ND-based tips and their basic properties are summarized. Then we discuss theoretically the concept of spatial resolution that is achievable in this special NSOM configuration and find it to be only limited by the scan height over the imaged system, in contrast with the standard aperture-tip NSOM whose resolution depends critically on both the scan height and aperture diameter. Finally, we describe a scheme we have introduced recently for high-resolution imaging of nanoplasmonic structures with ND-based tips that is capable of approaching the ultimate resolution anticipated by theory.

Unprecedented high modal gain of ~100 cmµ1 is obtained for an optimized structure based on InAs/InP quantum dashes (QDash) emitting at 1.55 µm. This structure allows achieving ~10 GHz direct modulation bandwidth. P-type doping reduces the Henry factor value down to 2.7.

Unprecedented high modal gain of ~100 cm-1 is obtained for an optimized structure based on InAs/InP quantum dashes (QDash) emitting at 1.55 μm. This structure allows achieving ~10 GHz direct modulation bandwidth. P-type doping reduces the Henry factor value down to 2.7.

We develop a semi-analytical method for analyzing surface plasmon interferometry using near-field scanning optical sources. We compare our approach to Young double hole interferometry experiments using scanning tunneling microscope (STM) discussed in the literature and realize experiments with an aperture near-field scanning optical microscope (NSOM) source positioned near a ring like aperture slit milled in a thick gold film. In both cases the agreement between experiments and model is very good. We emphasize the role of dipole orientations and discuss the role of magnetic versus electric dipole contributions to the imaging process as well as the directionality of the effective dipoles associated with the various optical and plasmonic sources.

We investigate the luminescence properties of 10 nm yttrium aluminum garnet (YAG) nanoparticles doped with Ce ions at 0.2%, 4% and 13% that are designed as active probes for scanning near-field optical microscopy. They are produced by a physical method without any subsequent treatment, which is imposed by the desired application. The structural analysis reveals the amorphous nature of the particles, which we relate to some compositional defects as indicated by the elemental analysis. The optimum emission is obtained with a doping level of 4%. The emission of the YAG nanoparticles doped at 0.2% is strongly perturbed by the crystalline disorder whereas the 13% doped particles hardly exhibit any luminescence. In the latter case, the presence of Ce(4+) ions is confirmed, indicating that the Ce concentration is too high to be incorporated efficiently in YAG nanoparticles in the trivalent state. By a unique procedure combining cathodoluminescence and Rutherford backscattering spectrometry, we demonstrate that the enhancement of the particle luminescence yield is not proportional to the doping concentration, the emission enhancement being larger than the Ce concentration increase. Time-resolved photoluminescence reveals the presence of quenching centres likely related to the crystalline disorder as well as the presence of two distinct Ce ion populations. Eventually, nano-cathodoluminescence indicates that the emission and therefore the distribution of the doping Ce ions and of the defects are homogeneous.

We investigate the luminescence properties of 10 nm YAG nanoparticles doped with Ce ions at 0.2 Scanning Near field Optical Microscopy. They are produced by a physical method without any subsequent treatment, which is imposed by the desired application. The structural analysis reveals the amorphous nature of the particles, which we relate to some compositional defect as indicated by the elemental analysis. The optimum emission is obtained with a doping level of 4 nanoparticles doped at 0.2 whereas the 13 case, the presence of Ce4+ ions is confirmed, indicating that the Ce concentration is too high to be incorporated efficiently in YAG nanoparticles in the trivalent state. By a unique procedure combining cathodoluminescence and Rutherford backscattering spectrometry, we demonstrate that the enhancement of the particles luminescence yield is not proportional to the doping concentration, the emission enhancement being larger than the Ce concentration increase. Time-resolved photoluminescence reveals the presence of quenching centres likely related to the crystalline disorder as well as the presence of two distinct Ce ions populations. Eventually, nano-cathodoluminescence indicates that the emission and therefore the distribution of the doping Ce ions and of the defects are homogeneous.

A nanodiamond (ND) hosting nitrogen-vacancy (NV) color centers is attached on the apex of an optical tip for near-field microscopy. Its fluorescence is used to launch surface plasmon-polaritons (SPPs) in a thin polycrystalline gold film. It is shown that the quantum nature of the initial source of light is preserved after conversion to SPPs. This opens the way to a deterministic quantum plasmonics, where single SPPs can be injected at well-defined positions in a plasmonic device produced by top-down approaches.

We address the issue of the second-order coherence of single surface plasmons launched by a quantum source of light into extended gold films. The quantum source of light is made of a scanning fluorescent nanodiamond hosting five nitrogen-vacancy (NV) color centers. By using a specially designed microscopy that combines near-field optics with far-field leakage-radiation microscopy in the Fourier space and adapted spatial filtering, we find that the quantum statistics of the initial source of light is preserved after conversion to surface plasmons and propagation along the polycrystalline gold film.

We report on spatially and spectrally-resolved linear optical properties induced by Direct Laser Writing in a prepared silver-doped phosphate glass, opening interesting possibilities for elementary photonics bricks. The formation mechanism of optical structures is proposed.

We demonstrate a simple scheme for high-resolution imaging of nanoplasmonic structures that basically removes most of the resolution limiting allowed light usually transmitted to the far field.This is achieved by implementing a Fourier lens in a near-field scanning optical microscope (NSOM) operating in the leakage-radiation microscopy (LRM) mode.The method consists of reconstructing optical images solely from the plasmonic 'forbidden' light collected in the Fourier space.It is demonstrated by using a point-like nanodiamond-based tip that illuminates a thin gold film patterned with a sub-wavelength annular slit.The reconstructed image of the slit shows a spatial resolution enhanced by a factor ≃ 4 compared to NSOM images acquired directly in the real space.

This paper describes the image formation process in optical leakage radiation microscopy of surface plasmon-polaritons with diffraction limited spatial resolution. The comparison of experimentally recorded images with simulations of point-like surface plasmon-polariton emitters allows for an assignment of the observed fringe patterns. A simple formula for the prediction of the fringe periodicity is presented and practically relevant effects of abberations in the imaging system are discussed.

A nanodiamond hosting two NV centers is attached onto the apex of an optical fiber-tip and illuminated by a laser light guided by the fiber itself. Gold films are dipped into the optical near field of the functionalized tip. The fluorescence light generated by the NVs efficiently launches surface plasmons that are imaged by near-field microscopy. Since the nanodiamond is a quasi single-photon source, we argue that single surface plasmons form the experimental images. This is a first step towards a “deterministic” quantum plasmonics where quantum plasmons can be launched at any freely chosen position in a plasmonic receptacle.

Leakage-radiation microscopy of a thin gold film demonstrates the ability of an ensemble of fluorescent diamond nanoparticles attached onto the apex of an optical tip to serve as an efficient near-field surface-plasmon polariton launcher. The implementation of the nanodiamond-based tip in a near-field scanning optical microscope will allow for an accurate control on the launching position, thereby opening the way to scanning plasmonics.

We demonstrate “deterministic” launching of propagative quantum surface-plasmon polaritons at freely chosen positions on gold plasmonic receptacles. This is achieved by using as a plasmon launcher a near-field scanning optical source made of a diamond nanocrystal with two nitrogen-vacancy color-center occupancy. Our demonstration relies on leakage-radiation microscopy of a thin homogeneous gold film and on near-field optical microscopy of a nanostructured thick gold film. Our work paves the way to future fundamental studies and applications in quantum plasmonics that require an accurate positioning of single-plasmon sources and may open a new branch in plasmonics and nanophotonics, namely scanning quantum plasmonics.

We discuss the concept of resolution in the context of our recent work [Opt. Express 17, 19969-19980 (2009)] in which the realization of a point-like scanning single photon near-field source (based on a single color center in a nano-diamond) was reported. We compare this new near-field optical microscope (NSOM) probe with usual aperture-NSOM probes. We conclude that the nanodiamond-based NSOM microscope has a resolving power which is only limited by the scan height over the imaged system. This contrasts with the aperture-NSOM resolution which also critically depends on the aperture diameter.